Epidemiology of Disappearing Plasmodium vivax Malaria: A Case Study in Rural Amazonia
Epidemiology of Disappearing Plasmodium vivax Malaria: A Case Study in Rural Amazonia
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DOI：
10.1371/journal.pntd.0003109
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发表时间：
2014-08-01
影响因子：
3.8
通讯作者：
Ferreira, Marcelo U.
中科院分区：
文献类型：
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作者：
Barbosa, Susana;Gozze, Amanda B.;Ferreira, Marcelo U.
背景：亚马逊盆地新的边境定居点对巴西消除疟疾构成重大挑战。在这里，我们描述了在占领巴西亚马逊地区雷曼西尼奥地区农业定居点的早期阶段疟疾的流行病学。我们检查了低密度和无症状寄生虫在传播率下降期间对间日疟原虫总负担的相对贡献，并讨论了在雷曼西尼奥和类似环境下消除疟疾的潜在障碍。方法：在雷曼西尼奥进行了8次社区范围的横断面调查，涉及584名受试者，历时3年，并在调查期间进行了积极和被动的发热疾病监测。我们用定量聚合酶链式反应检测常规显微镜漏检的低密度无性寄生虫病和配子体寄生虫。采用多因素Logistic回归模型分析间日疟原虫感染和发病的独立危险因素。主要研究结果/结论：间日疟原虫患病率从2010年3-4月的23.8%下降到2013年4-5月的3.0%，2011年3-4月后未发现恶性疟原虫感染。尽管来自无疟疾地区的移民患疟疾的风险增加，但他们感染间日疟原虫和患病的几率随着居住在亚马逊地区的每一年而下降2-3%。一些研究结果表明，低密度和无症状间日疟原虫可能会使雷曼辛霍地区残留的间日疟原虫消灭工作复杂化：(A)随着间日疟原虫传播率的下降，次专利感染(即镜检未检出)的比例从43.8%增加到73.1%；(B)大多数(56.6%)间日疟原虫感染是无症状的，其中32.8%既是次专利感染又是无症状感染；(C)无症状间日疟原虫携带者占宿主种群间日疟原虫总生物量的54.4%；(D)超过90%的亚专利和无症状间日疟原虫有可通过PCR检测到的配子体；和(E)极少数(17.0%)未经治疗的无症状和亚显症间日疟原虫感染在6周的随访中发展为临床疾病，并可通过常规疟疾监测发现。
Background: New frontier settlements across the Amazon Basin pose a major challenge for malaria elimination in Brazil. Here we describe the epidemiology of malaria during the early phases of occupation of farming settlements in Remansinho area, Brazilian Amazonia. We examine the relative contribution of low-density and asymptomatic parasitemias to the overall Plasmodium vivax burden over a period of declining transmission and discuss potential hurdles for malaria elimination in Remansinho and similar settings.Methods: Eight community-wide cross-sectional surveys, involving 584 subjects, were carried out in Remansinho over 3 years and complemented by active and passive surveillance of febrile illnesses between the surveys. We used quantitative PCR to detect low-density asexual parasitemias and gametocytemias missed by conventional microscopy. Mixed-effects multiple logistic regression models were used to characterize independent risk factors for P. vivax infection and disease.Principal Findings/Conclusions: P. vivax prevalence decreased from 23.8% (March-April 2010) to 3.0% (April-May 2013), with no P. falciparum infections diagnosed after March-April 2011. Although migrants from malaria-free areas were at increased risk of malaria, their odds of having P. vivax infection and disease decreased by 2-3% with each year of residence in Amazonia. Several findings indicate that low-density and asymptomatic P. vivax parasitemias may complicate residual malaria elimination in Remansinho: (a) the proportion of subpatent infections (i. e. missed by microscopy) increased from 43.8% to 73.1% as P. vivax transmission declined; (b) most (56.6%) P. vivax infections were asymptomatic and 32.8% of them were both subpatent and asymptomatic; (c) asymptomatic parasite carriers accounted for 54.4% of the total P. vivax biomass in the host population; (d) over 90% subpatent and asymptomatic P. vivax had PCR-detectable gametocytemias; and (e) few (17.0%) asymptomatic and subpatent P. vivax infections that were left untreated progressed to clinical disease over 6 weeks of follow-up and became detectable by routine malaria surveillance.